Skip to content
Free public beta until December 4, 2026: every course is open, no card needed. After that, the first chapter of each course stays free and full access is a one-time $39 ($19 for up to 100 founding members chosen for helpful feedback). Your progress is kept. How the beta works

daylight saving time

Moving clocks forward in spring and back in autumn, which makes some local times skip or repeat.

A seasonal change of a zone's offset that creates invalid (skipped) and ambiguous (repeated) local times.

Examples

  • In New York on 8 March 2026, clocks jump from 01:59 to 03:00, so 02:30 that night never happens.

See also

time zone UTC
Read the full section →